Field of the Invention
This invention relates to an electrical device containing luminescent diodes. In particular, an electrical device having pixel circuits for organic light emitting diodes, the organic light emitting diodes resulting from liquid deposition of organic semiconductor material on a backplane. More particularly, the incorporation of resistors into a multitude of pixel circuits thereby masking systematic luminance variation resulting from off-specification liquid deposition of luminescent materials. The electrical device containing luminescent diodes, also called a display device, can be mounted on the backplane containing a rigid or flexible substrate. The backplane typically contains electrical elements for pixel circuits and may also include thin film transistors for each pixel. Deposition of organic semiconductor materials on these backplanes, including liquid phase deposition, can produce non-uniformities in the resultant luminescent pixel light output, color, or other characteristics, which are collectively referred to as systematic variations, usually appearing in some fashion of patterned irregularities.
The application of resistors having distinct values in a multitude of pixel circuits provides a random variation, to combine with the systematic variation to mask luminance irregularities. The resulting display device provides increased manufacturing tolerance and improved yield for display devices.
Description of the Related Art
One option of an electronic device can include an organic light-emitting diode (OLED) display, or the like. OLED display devices utilizing one or more layers of organic semiconductor materials laminated with other supporting layers and sandwiched by two electrodes are used in many different kinds of electronic equipment. Manufacturing of these OLED electronic devices may be performed using solution deposition techniques. One process of making OLED electronic devices is to deposit organic layers over the substrate, also referred to as the backplane when containing electronic elements, by printing (e.g., ink-jet printing, continuous printing, etc.). In a printing process, the liquid composition being printed includes an organic material in a solution, dispersion, emulsion, or suspension with an organic solvent, with an aqueous solvent, or with a combination of solvents. After printing, the solvent(s) is(are) evaporated and the organic material remains to form an organic layer for the electronic device.
Liquid printing can be conducted in either non-continuous or continuous operation as disclosed in the prior art. The deposition of the liquid composition in either a continuous or non-continuous method may lead to non-uniformities in the resultant layer upon drying on the backplane. Specifically, as the liquid composition dries solvent diffuses into the surrounding environment. These non-uniformities often appear as a pattern of irregularities in the final luminescent pixels, and these patterns of irregularities are often referred to as systematic variations. While various techniques are used to minimize these systematic variations, problems persist with the manufacturing losses associated with scrapping these off-specification electronic devices.
In view of the foregoing it is believed additional improvement is required to optimize organic electronic devices.